In the operation of modern internal combustion engines, an oil baffle box, in which an oil suction space is defined, is provided inside the oil pan. The lubricating oil returned from the consumer locations within the internal combustion engine is usually sent back to areas outside the oil suction space before it passes over into the oil suction space through openings in the oil baffle box, these openings being controlled by flaps.
An oil pan into which two oil baffle walls are inserted is known from DE 101 39 709 A1. Each of the oil baffle walls is provided with two window-like through-openings, each of which is controlled by two flow flaps functioning as a nonreturn valve. Hold-down pins are provided to fasten the flow flaps to the baffle walls.
So that the baffle box inside an oil pan can fulfill its function, the flaps are usually made of elastomeric material, which expands as a result of its continuous contact with the lubricating oil. This swelling capacity means that the sealing function of such flaps is no longer guaranteed. When a swelling process such as this occurs, the flaps expand in all directions, with the result that they become bent out of shape, which impairs the sealing function of flaps of this type.